1. Field of the Invention:
The invention relates to a process for operating an Otto engine, i.e., a spark ignition four-cycle engine equipped with a carburetor, with a non-leaded liquid fuel, containing an addition of 1 to 100, preferably 5 to 20 ppm, by weight of ferrocene.
2. Discussion of the Background:
In recent years, the industrial countries have passed laws to restrict the emissions from internal combustion engines of, in particular, carbon monoxide (CO), nitrogen oxides (NO.sub.x) and hydrocarbons (C.sub.x H.sub.y) in order to limit environmental pollution that is related to these emissions. Even the lead compounds, for example tetraethyl lead, that are added as knock suppressors to fuels for Otto engines, are subject to increasing restrictions with respect to their use.
The unwanted exhaust gas emissions can be controlled at three different points during the function of the engine. The first point at which the emissions may be affected is the mixture formation stage prior to burning of the fuel. The second point at which the emissions composition may be altered is within the engine itself, for example by effecting specific design changes to optimize the combustion chamber, etc. Finally, the third possibility is an aftertreatment of the exhaust gases as they pass out of the engine following combustion. Typically, a catalytic converter is used to promote the after burning of CO and hydrocarbons to harmless carbon dioxide and water. At the same time, the catalytic converter reduces the oxides of nitrogen present in the exhaust gas to neutral nitrogen. Using a catalytic converter, approximately 90% or more of the toxic carbon monoxide, hydrocarbons and oxides of nitrogen can be converted to harmless materials. Of the solutions developed to clean or reduce car emissions, the catalytic processes have become very important (see Chemist Newspaper, 97 Year 1973, no. 9, p. 469 ff.). The addition of lead to leaded fuels poisons the exhaust gas catalytic converters, however, rendering them ineffective by coating the active centers of the catalytic converter.
Due to the health-impairing effect of lead compounds contained in the combustion exhausts emitted during operation of Otto engines, alternatives have been sought that would exhibit not only the beneficial effect of adding lead compounds, in particular improved anti-knock behavior, but also a specific beneficial effect with respect to the wear of the exhaust valves of four cycle Otto engines.
Thus blends of liquid hydrocarbon, containing primarily gasoline and an organometal compound selected from the group of dicyclopentadienyl iron (ferrocene) and gasoline-soluble derivatives, have been proposed to reduce the consumption of fuel and the pollution from exhaust as well as to eliminate or reduce the carbon deposits, where such blends also contain the usual anti-knock additives (see DE-OS 25 02 307).